• A unified expression for liquid holdup and pressure drop in micro-packed beds is proposed, covering both organic and aqueous liquid phases.
• For gas-organic systems, liquid holdup ranges from 0.5 to 0.8 and pressure drop from 50 to 350 kPa·m−1, significantly higher than in traditional trickle beds.
• A strong correlation between liquid holdup and pressure drop is established for the first time, enabling a general pressure drop prediction model.
• The model accounts for two-phase flow rate, viscosity, and packing particle size, facilitating reliable design of micro-packed bed reactors for industrial applications.